minor symfony#19539 [VarDumper] Relax 1 test failing with latest PHP versions (fabpot, remicollet)

This PR was merged into the 2.8 branch.

Discussion
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[VarDumper] Relax 1 test failing with latest PHP versions

| Q             | A
| ------------- | ---
| Branch?       | 2.8
| Bug fix?      | no
| New feature?  | o
| BC breaks?    |  no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | N/A
| License       | MIT
| Doc PR        | reference to the documentation PR, if any

Related to php bug https://bugs.php.net/72646 which is fixed in 5.6.25RC1, 7.0.10RC1, 7.1.0beta2

Detected in Fedora CI, failed since 7.0.10RC1, see
https://apps.fedoraproject.org/koschei/package/php-symfony

Commits
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6703b41 Relax 1 test failing with latest PHP versions
eabbcf0 bumped Symfony version to 2.8.10

Author: nicolas-grekas

src/Symfony/Component/VarDumper/Tests/Caster/SplCasterTest.php

@@ -94,10 +94,10 @@ public function testCastFileObject()
   file: true
   dir: false
   link: false
-%AcsvControl: array:2 [
+%AcsvControl: array:%d [
     0 => ","
     1 => """
-  ]
+%A]
   flags: DROP_NEW_LINE|SKIP_EMPTY
   maxLineLen: 0
   fstat: array:26 [